Problem: Simplify the following expression: $z = \dfrac{p}{3} - \dfrac{p}{2}$
Explanation: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $3$ and $2$ $\lcm(3, 2) = 6$ $ z = \dfrac{2}{2} \cdot \dfrac{p}{3} - \dfrac{3}{3} \cdot \dfrac{p}{2} $ $z = \dfrac{2p}{6} - \dfrac{3p}{6}$ $z = \dfrac{2p -3p}{6}$ $z = \dfrac{-p}{6}$